Concrete is one of the most utilized man-made materials in the world. Concrete includes cement and an aggregate or filler. Cements can generally be classified as non-hydraulic and hydraulic. Typical non-hydraulic cements harden by carbonation in the presence of carbon dioxide in the air. Hydraulic cements such as Portland cement, on the other hand, harden through the hydration of silicates, oxides, aluminates, aluminoferrites, and sulfates present in the cement.
Non-hydraulic cements derived from the reaction between carbon dioxide and silicates such as magnesium silicate and calcium silicate have been an area of interest. For example, non-hydraulic cements absorb large amounts of carbon dioxide as they harden, making them an environmentally friendly choice for use in sustainable materials. However, diffusion of carbon dioxide and subsequent carbonation of a non-hydraulic cement may take for example, up to 18 hours before sufficient green strength develops in the composition. It is advantageous to be able to demold products comprising the non-hydraulic cement quickly and recycle the mold to production. This would mean that fewer molds would be required and that production rates could be increased. There is a continuing desire for cementitious compositions that are environmentally friendly and can provide rapid green strength.